Pressure-sensitive adhesive sheet

ABSTRACT

Provided is a PSA sheet that allows installation of a protection sheet with good shape precision on the surface of an object to be protected. The PSA sheet provided by this invention comprises a substrate whose primary component is a resin film and a PSA layer placed on one face of the substrate. The PSA sheet comprises a protection sheet part which is adhered to an adherend to protect it, a marginal part bounded from the protection sheet part by a tear-off line surrounding the protection sheet part, and a tear-aiding structure provided along the tear-off line. The PSA sheet is configured so that after the protection sheet part is adhered to the adherend, when the marginal part is pulled in a direction in which the PSA sheet is peeled off the adherend, the marginal part is tom off the protection sheet part.

CROSS-REFERENCE

The present invention claims priority to Japanese Patent Application No.2016-142776 filed on Jul. 20, 2016; and the entire contents thereof areincorporated herein by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a pressure-sensitive adhesive sheet, inparticular, a pressure-sensitive adhesive sheet comprising a protectionsheet part which is to be applied to an adhered to protect it.

Description of the Related Art

For surfaces of metal plates, painted steel plates, synthetic resinplates, etc., to prevent damage such as scratches and dirt deposits, itis known to apply protection sheets thereto for protection. Such aprotection sheet generally has a pressure-sensitive adhesive (PSA) on afirst face of a substrate sheet formed from resin film, etc. Via thePSA, the protection sheet is adhered to an adherend (an object to beprotected) to cover the adherend surface so that it can achieve theprotection purpose. Technical documents related to protection sheetsinclude Japanese Patent No. 5203593 and Japanese Patent ApplicationPublication No. 2007-50622.

SUMMARY OF THE INVENTION

It is generally desirable that a protection sheet has a shape suited tothe protected region in an object to be protected. In this aspect,Japanese Patent No. 5203593 discloses an applicator sheet that comprisesan adhesive sheet formed inside a row of cut holes as well as anunneeded part surrounding the adhesive sheet, and by pulling theunneeded part in the width direction, the adhesive sheet and theunneeded part can be separated. However, in the art according toJapanese Patent No. 5203593, the shape precision of the separatedadhesive sheets tends to be either low or inconsistent. Japanese PatentApplication Publication No. 2007-50622 discloses a vehicle-protectinglaminate film provided with a tear-off perforation along the boundarybetween a vehicle-covering part and an anti-deformation part extendingfrom one edge of the vehicle-covering part. However, since thevehicle-protecting laminate film is pre-cut, customized to the shape ofa designated part, its periphery is likely to collect dust, etc. Asanother problem, while being applied to an adherend, the adhesive faceof the vehicle-covering part is likely to be directly touched andcontaminated by fingers of a worker.

The present invention has been made in view of such circumstances withan objective to provide a PSA sheet that allows for an efficientinstallation of a protection sheet with excellent shape precision on thesurface of an object to be protected.

The present description provides a PSA sheet comprising a substrate anda PSA layer placed on one side of the substrate. The PSA sheet comprisesa protection sheet part to be adhered to an adherend to protect it, amarginal part bounded from the protection sheet part by a tear-off linesurrounding the protection sheet part. The PSA sheet comprises atear-aiding structure, or a tear-aiding structural feature, providedalong the tear-off line. The substrate comprises a resin film as theprimary component. The PSA sheet is configured so that after theprotection sheet part is adhered to an adherend, when the marginal partis pulled in a direction (a peel direction) in which the PSA sheet ispeeled off the adherend, the marginal part is tom off the protectionsheet part.

In the PSA sheet in this embodiment, the protection sheet part is aregion that is used to protect the adherend and forms a separateprotection sheet when the marginal part is tom off. With the PSA sheet,the operation as easy as applying the protection sheet part to anadherend followed by pulling the marginal part (the area surrounding theprotection sheet part) in a direction in which the PSA sheet is peeledoff the adherend, the marginal part can be torn off with high precision.Thus, it makes it possible to efficiently realize a situation that anadherend surface to which a protection sheet with excellent shapeprecision is adhered. Because the marginal part is provided surroundingthe protection sheet part, a worker can make placement adjustments(positioning) or redo the application, if necessary, by holding themarginal part of the PSA sheet. Thus, incidents of directly touching theadhesive face of the protection sheet part with the worker's finger,etc., can be avoided to prevent degradation of the protective functioncaused by contamination of the adhesive face. The protection sheet partsurrounded by the marginal part is also preferable from the standpointof preventing accumulation of dust and the like on the periphery of theprotection sheet part of the PSA sheet before used.

In a preferable embodiment of the PSA sheet, the surface (adhesive face)of the PSA layer may be separably in contact with the back face (theface on the reverse side of the adhesive face, typically the second faceof the substrate) of the PSA sheet, whereby the adhesive face isprotected. In such an embodiment, the PSA sheet can be free of aseparate release liner. The PSA sheet in such an embodiment can beadvantageous in terms of workability because its application to anadherend requires no release liner separation or removal; it is alsopreferable from the standpoint of reducing wastes.

Specific examples of the embodiment where the adhesive face is separably(releasably) in contact with the back face of the PSA sheet include alaminate form where two or more PSA sheets are layered with the adhesiveface of one PSA sheet placed in contact with the back face of anotherPSA sheet, and a roll form where a long PSA sheet is wound in a rollwith its adhesive face in contact with its back face.

The PSA sheet according to a preferable embodiment is long and wound ina roll, comprising a plurality of protection sheet parts seriallyarranged in the length direction of the PSA sheet. With respect to thePSA sheet in such an embodiment, protection sheets can be installed ontwo or more adherends efficiently and precisely by repeating theprocedure including the followings; a required length is dispensed fromthe roll form, the protection sheet part is adhered to an adherend, andthe marginal part is torn off.

The PSA sheet disclosed herein preferably comprises at least a cut holeor a groove as the tear-aiding structure. By this, the marginal part canbe easily and precisely torn off the protection sheet part.

In a preferable embodiment, the tear-aiding structure comprises at leasta groove running along the tear-off line. With such a groove, when theprotection sheet is applied to an adherend and the PSA sheet is pulledin the peel direction, the PSA sheet tends to be precisely tom off inthe thickness direction along the groove to form a protection sheet witha smooth periphery.

In an embodiment where the tear-aiding structure includes a groove, theresin material forming the groove bottom in the substrate preferablyexhibits a tensile modulus of 300 MPa or greater. By this, the PSA sheetcan be sharply torn off along the groove, and the shape precision andthe appearance quality of the protection sheet tends to improve.

In an embodiment of the PSA sheet disclosed herein, as the substrate, asubstrate comprising a polyolefinic resin film can be preferably used.This tends to increase the curved surface conformability of the PSAsheet.

In the PSA sheet disclosed herein, the protection sheet part preferablyexhibits a 180° peel strength of 3 N/25 mm or greater. When the peelstrength is at or above the prescribed value, the operation of applyingthe protection sheet part to an adherend and pulling the marginal partin the peel direction to tear it off can be stably carried out. This canincrease the ease of tearing off the marginal part and the precision oftearing.

The PSA sheet disclosed herein may comprise a plurality of applicationunits divided by separation lines. Here, each application unit comprisesat least one each of the protection sheet part and the marginal partsurrounding the protection sheet part. When the PSA sheet in such anembodiment is used, by carrying out application to adherends and tearingunit by unit, protection sheets can be installed on the adherendsefficiently and precisely.

When the PSA sheet is long and wound in a roll, a plurality ofapplication units can be serially arranged in the length direction ofthe PSA sheet divided by separation lines running across the width ofthe PSA sheet. With respect to the PSA sheet in such an embodiment, forinstance, a length corresponding to one application unit is dispensedfrom the roll form; after or before the protection sheet part is appliedto an adherend, the application unit is tom off along the separationline to separate it from the next application unit; the marginal part istorn off the protection sheet part; the preceding procedure is repeatedto efficiently and precisely install protection sheets on a plurality ofadherends.

The PSA sheet disclosed herein can be provided with a positioningassistant to assist positioning of the PSA sheet. By this, an adherendand a protection sheet part can be efficiently aligned to facilitate thework. In a preferable embodiment, the positioning assistant can beprovided to the marginal part of the PSA sheet. The positioningassistant thus provided to the marginal part can facilitate thepositioning work while minimizing influences on the performance of theprotection sheet part.

The present description provides a method for producing a protectionsheet-bearing member in which a protection sheet is adhered to thesurface of the member. The production method includes obtaining a PSAsheet that comprises a substrate whose primary component is a resin filmand a PSA layer placed on a first face of the substrate. The PSA sheetcomprises a protection sheet part to be adhered to an adherend toprotect it, a marginal part bounded from the protection sheet part by atear-off line surrounding the protection sheet part, and a tear-aidingstructure provided along the tear-off line. The production method alsoincludes adhering the protection sheet part to the member, and pullingthe marginal part in a direction in which the PSA sheet is peeled offthe member, thereby tearing the marginal part off the protection sheetpart and leaving the protection sheet part on the member. According tosuch a production method, a protection sheet formed of the protectionsheet part can be precisely and efficiently applied to the surface of amember. Thus, high-quality protection sheet-bearing members can beproduced efficiently.

This description provides a method for applying a protection sheet tothe surface of a member. The application method includes obtaining a PSAsheet that comprises a substrate whose primary component is a resin filmand a PSA layer placed on a first face of the substrate. The PSA sheetcomprises a protection sheet part to be adhered to an adherend toprotect it, a marginal part bounded from the protection sheet part by atear-off line surrounding the protection sheet part, and a tear-aidingstructure provided along the tear-off line. The application method alsoincludes adhering the protection sheet part to the member, and pullingthe marginal part in a direction in which the PSA sheet is peeled offthe member, thereby tearing the marginal part off the protection sheetpart and leaving the protection sheet part on the member. According tosuch an application method, a protection sheet formed of the protectionsheet part can be precisely and efficiently applied to the surface of amember.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example of how the PSA sheetaccording to an embodiment can be used.

FIG. 2 is a cross-sectional diagram at line II-II in FIG. 1.

FIG. 3 is a diagram illustrating an example of how the PSA sheetaccording to an embodiment can be used.

DETAILED DESCRIPTION OF THE INVENTION

Preferred embodiments of the present invention are described below.Matters necessary to practice this invention other than thosespecifically referred to in this description may be understood to aperson ordinarily skill in the art based on the disclosures aboutembodiments of the invention according to the present description andcommon technical knowledge at time the application was filed. Thepresent invention can be implemented based on the contents disclosedherein and common technical knowledge in the subject field. In thedrawings referenced below, a common reference numeral may be assigned tomembers or sites producing the same effects, and redundant descriptionsmay be omitted or simplified. The embodiments in the drawings areschematically illustrated for clearly describing the present invention,and do not necessarily represent the dimensions or scales of an actualproduct.

An embodiment of the PSA sheet disclosed herein is described withreference to drawings.

A PSA sheet 1 shown in FIG. 1 comprises a protection sheet part 2 to beapplied to an adherend 90 which is an object subject to protection, anda marginal part 4 bounded from the protection sheet part 2 by a tear-offline 3 surrounding the protection sheet part 2. Protection sheet part 2has a shape corresponding to the protected region in adherend 90. In theexample shown in FIG. 1, protection sheet part 2 has an identicalrectangular shape as the top face of adherend 90 having a rectangularboard shape. PSA sheet 1 is configured so that by tearing the marginalpart 4 off (apart from) the protection sheet part 2 along the tear-offline 3, a separate protection sheet is formed with a peripheral shapecorresponding to the protected region. As used herein, that the tear-offline surrounds the protection sheet part means that 50% or more(typically 60% or more. e.g. 75% or more) in length of the circumferenceof the protection sheet formed from the protection sheet part isadjacent to the marginal part, bounded by the tear-off line. Thus, thePSA sheet disclosed herein is not limited to an embodiment such as thePSA sheet 1 in FIG. 1 where the entire circumference of protection sheetpart 2 is surrounded by the tear-off line 3. For instance, it can alsobe in an embodiment where a rectangular protection sheet part issurrounded on three sides by a marginal part, along with a tear-offline, with the remaining one side forming an outer edge of the PSAsheet. Alternatively, the remaining one side may be designated as aseparation line that divides application units described later. That is,part of the tear-off line may also serve as the separation line. In apreferable embodiment, the protection sheet part is surrounded on theentire circumference by the tear-off line.

PSA sheet 1 comprises a substrate 10 and a PSA layer 50 placed on afirst face 10A thereof. Substrate 10 has a release face on a second face(back face) 10B of substrate 10. Substrate 10 comprises a monolayer ormultilayer (i.e. two-layer or higher, the same applies hereafter) resinfilm as the primary component. As the multilayer resin film, as shown inFIG. 2, a three-layer resin film can be preferably used, the three-layerresin film having a front layer 12 forming the first face 10A ofsubstrate 10, a back layer 16 forming the back face 10B of thesubstrate, and a middle layer 14 placed between them. Although the PSAlayer 50 is typically formed in a continuous manner, it may be formed ina random or regular pattern of dots, stripes, etc., depending on thepurpose and application. The PSA layer 50 can be provided at leastpartially to the protection sheet part 2 (typically at least to anannular part along the circumference of the protection sheet part 2);the marginal part 4 may be partially or entirely free of the PSA layer50. In an embodiment preferable from the standpoint of the productivityof PSA sheets 1, the PSA layer 50 is provided to the entire area of thefirst face 10A of substrate 10. In another preferable embodiment, thePSA layer 50 is provided to the entire area of the protection sheet part2 in the first face 10A of substrate 10 and to areas of the marginalpart 4 adjacent to the protection sheet part 2, but not to a border areaof the marginal part 4 along one or each edge of the length direction(one or each widthwise edge) of substrate 10.

The PSA sheet 1 includes a tear-aiding structure 30 provided along thetear-off line 3, that is, on the line in accordance with the tear-offline 3. By this, with the protection sheet part 2 adhered to anadherend, the marginal part 4 of the PSA sheet 1 is pulled in the peeldirection, the PSA sheet 1 undergoes tearing in the thickness directionalong the tear-off line 3 and the marginal part 4 is torn off theprotection sheet part 2, whereby the remaining protection sheet part 2forms a protection sheet on the adherend. In the example shown in FIG.1, the tear-aiding structure comprises perforations 32, slits 34 andgrooves 36 in combination. Here, perforations 32 and slits 34 are thoughholes (cut holes) in substrate 10. Grooves 36 are depressions formed tocertain depths, but not all through substrate 10 and can be provided tothe first face 10A side of substrate 10, to the second face (back face)10B side, or to each side. In the example shown in FIG. 1, grooves 36are incised marks formed by allowing a machine blade to penetratesubstrate 10 to a depth equivalent to about three-fourth the thicknesson the second face 10B side of substrate 10. They can be thought asnarrow V-shaped grooves.

In the example shown in FIG. 1, perforations 32, slits 34 and grooves 36forming the tear-aiding structure 30 are arranged in particular asfollows: On the rectangular tear-off line 3, perforations 32 are formedover the entire lengths of short sides 3A and 3C. For each of long sides3B and 3D, slits 34 are formed at both ends and a groove 36 is formed toconnect the slits 34. By this, as shown in FIG. 2, in the cross sectiontaken along the long side 3B in the tear-off line 3, at both ends oflong side 3B, slits 34 as through holes in substrate 10 are providedbetween the protection sheet part 2 and the marginal part 4. Between theslits 34, the protection sheet part 2 and the marginal part 4 areconnected at the bottom 36A of the groove 36. The cross section takenalong the long side 3D also has the same structure. The protection sheetpart 2 and the marginal part 4 of the PSA sheet 1 are connected at thebottom 36A of groove 36 and also between cut holes forming perforations32 arranged at short sides 3A and 3C.

The PSA sheet 1 shown in FIG. 1 is long and wound in a roll with thesurface (adhesive face) 1A of the PSA layer 50 separably in contact withthe back face 10B of substrate 10, which is also the back face 1B of thePSA sheet 1 in this embodiment, to form a PSA sheet roll 100. That is.PSA sheet roll 100 is free of a release liner, apart from the PSA sheet1. With respect to such a release liner-free PSA sheet roll 100, whenthe PSA sheet 1 is dispensed from the PSA sheet roll 100, the adhesiveface 1A is exposed upon separation from the back face 10B of thesubstrate. Thus, apart from dispensing the PSA sheet 1, it isunnecessary to remove any release liner to expose the adhesive face 1A,whereby application of the PSA sheet 1 is facilitated. The PSA sheetroll 100 free of a release liner is preferable also from the standpointof making the PSA sheet roll 100 lighter in weight to reduce the load ona worker and of making the PSA sheet 1 longer to reduce the frequency ofchanging PSA sheet rolls 100. It is also preferable in view of savingresources.

The PSA sheet 1 forming the PSA sheet roll 100 comprises two or moreapplication units arranged serially in the length direction of the PSAsheet 1. FIG. 1 shows two application units 100A and 100B of the PSAsheet 1 from the outer end of the roll. A protection sheet part 2 and amarginal part 4 described earlier are formed in each application unit.According to the PSA sheet 1 in such an embodiment, by applyingprotection sheet parts 2 and tearing off marginal parts 4 unit by unit,protection sheets formed with protection sheet parts 2 can be installedon the surfaces of adherends 90 efficiently and precisely. FIG. 1 showsan example of an embodiment where one application unit has oneprotection sheet part, but it is not limited to this. It can be in anembodiment where one application unit includes two or more protectionsheet parts.

Between the respective application units, separation lines 102 aremarked across the width of the PSA sheet 1. Cutting the PSA sheet 1along the separation lines 102 at appropriate timings may facilitateunit-by-unit application of protection sheet parts 2 and tearing ofmarginal parts 4. The PSA sheet 1 is preferably provided with aseparation-aiding structure 120 along a separation line 102. With theseparation-aiding structure 120, each application unit can be torn offalong the separation line 102 without the use of a cutting device suchas a cutter. The separation-aiding structure 120 can be formed of, forinstance, a perforation, a slit, a groove, or a combination of these,similarly to the tear-aiding structure 30. In the example shown in FIG.1, a separation-aiding structure 120 is constituted with a perforationformed over the entire length of the separation line 102. Alternatively,in some embodiments, application units can be separated using a suitablecutting device in absence of such a separation-aiding structure.

In each of marginal parts 4 of application units 100A and 100B, there isformed a positioning assistant 42 useful when placing the protectionsheet part 2 on an adherend 90. In the example shown in FIG. 1, thepositioning assistant 42 is an approximately circular through hole. Forinstance, alignment of the protection sheet part 2 and adherend 90 canbe facilitated by allowing a columnar alignment guide (not shown in thedrawing) provided to a designated location on the adherend 90 to passthrough the through hole. In the example shown in FIG. 1, a total of twothrough holes per one application unit are provided as positioningassistants. These two though holes are arranged in the marginal part 4on the fore edge side (closer to the outer end of the roll) relative tothe protection sheet part 2, near the two lengthwise edges of the PSAsheet 1 (one through hole at each edge). The arrangement or the numberof positioning assistants 42 is not, however, limited to this.

The PSA sheet 1 in such an embodiment can be favorably used, forinstance, in the following manner: As shown in FIG. 1, one applicationunit is dispensed from the PSA sheet roll 100 and the application unit10 (A at the fore end of the PSA sheet 1 is spread over an adherend 90with some space left between itself and the top face (the protectedface) of the adherend 90. The adherend 90 can be an automobileconstituent member (e.g. an exterior plate or a pillar of a vehicle).The positioning assistants 42 of application unit 100A are set onalignment guides not shown in the drawing to align the adherend (member)90 and the protection sheet part 2. Here, as necessary, the placementcan be corrected or finely adjusted by holding the marginal part 4. Theprotection sheet part 2 is then adhered to the adherend 90. Although noparticular limitations are imposed, the adhesion procedure can becarried out so that, for instance, press-bonding the protection sheetpart 2 onto the adherend 90 proceeds from the fore end (in FIG. 1, fromthe end of the PSA sheet 1 closer to the viewer) towards the rear end ofthe protection sheet part 2. The protection sheet part can bepress-bonded, using an applicator such as a squeegee as necessary.

After the protection sheet part 2 is adhered to the adherend 90, the PSAsheet 1 is cut along the separation line 102 dividing the applicationunits 100A and 100B. The application unit 100A is thereby tom off therest of the PSA sheet 1. As shown in FIG. 3, when the marginal part 4 ispulled in a direction in which the PSA sheet 1 (the application unit100A here) is peeled off the adherend 90, by the adhesive strength ofthe protection sheet part 2 to the adherend 90 and the tear-aidingstructure 30, the marginal part 4 is torn off along the tear-off line 3,leaving the protection sheet part 2 on the adherend 90. The remainingprotection sheet part 2 forms the protection sheet to protect theadherend 90. The adherend 90 bearing the protection sheet on the surface(a protection sheet-bearing member) can be thus obtained.

Subsequently, a new adherend 90 is set up; the next one application unitis dispensed from the PSA sheet roll 100; using the application unit100B at the fore end of the PSA sheet 1, a protection sheet is placed onthe surface of the adherend 90, in a similar manner as with theapplication unit 100A. By repeating this, using the PSA sheet roll 100,protection sheets can be efficiently installed on a plurality ofadherends 90.

For pulling the marginal part 4 in a direction in which the PSA sheet 1is peeled off the adherend 90, typically in a direction at a right angleto the surface of the adherend 90, the pulling angle (the angle betweenthe pulling direction and the surface of the adherend 90) is notparticularly limited as long as it enables tearing of the marginal part4, leaving the protection sheet part 2 on the adherend 90. The pullingangle can be, for instance, 30° or larger (preferably 45° or larger) tothe surface of the adherend 90. From the standpoint of inhibitinglifting of the protection sheet part 2 caused by the pulling, thepulling angle is usually suitably 60° or larger. From the standpoint ofincreasing the tearing precision by efficiently tearing the PSA sheet 1along the tear-off line 3 (typically by tearing the PSA sheet 1 in thethickness direction), the pulling angle is preferably 90° or larger(e.g. larger than 9), or it can be 105° or larger, or even 120° orlarger (e.g. 1350 or larger). The maximum pulling angle is notparticularly limited. From the standpoint of the workability, it isusually suitably smaller than 180° (e.g. 160° or smaller).

Although no particular limitations are imposed, it is preferable thatthe marginal part 4 is pulled in a direction generally running along thelength direction (e.g. in a direction at an angle of up to 30° to thelength direction, preferably up to 15°, e.g. up to 10°). This tends toincrease the tearing precision. When the length direction of the PSAsheet 1 generally coincides with the length direction of the PSA sheetpart 2 as shown in FIG. 1, the marginal part 4 can be tom off, startingfrom the fore end side of the PSA sheet 1 (in FIG. 1, from the viewer'sside) or from the rear end side. From the standpoint of the workability,as in the example shown in FIG. 3, in a preferable embodiment, the PSAsheet 1 is cut off at the rear end of the application unit 100A alongthe separation line 102 shown in FIG. 1, and subsequently, the rear endof the marginal part 4 is pulled towards the fore end to start tearingoff the marginal part 4 starting from the rear end side.

In the example described above, after the protection sheet part 2 isadhered to the adherend 90, the application unit 100A is torn off therest of the PSA sheet 1 (i.e. the application unit 100B and thefollowing portion). However, the application unit 100A can be adhered tothe adherend 90 after the application unit 100A is torn off the PSAsheet 1. From the standpoint of the ease of handling (e.g. the ease ofapplication) of the PSA sheet 1, when the application unit 100A is, forinstance, 15 cm or longer (especially 30 cm or longer), it is preferableto select an embodiment where the application unit 100A is tom off thePSA sheet 1 after the protection sheet part 2 is adhered to the adherend90. According to such an embodiment, because the rear end of theapplication unit 100A is connected to the rest of the PSA sheet 1, byholding the application unit 100A with a tension force applied acrossthe PSA sheet roll 100 and the application unit 100A (more specifically.e.g. a positioning assistant 42), wrinkling and twisting of theprotection sheet part 2 can be prevented. In view of preventingcontamination of the protection sheet part 2, it is also preferable toapply the protection sheet part 2 to the adherend 90 before cutting theapplication unit 100A off the rest of the PSA sheet 1.

In the embodiment shown in FIG. 1, the tear-aiding structure 30 isprovided only on the tear-off line 3, but not to the inside or outsideof the tear-off line 3. Thus, the PSA sheet 1 is free of cut holes suchas a perforation or slits inside the tear-off line, that is, in therange of the protection sheet part 2. In such an embodiment, theprotection sheet formed from the protection sheet part 2 can providesgood protection. In absence of a tear-aiding structure placed off to theinside or outside of the tear-off line, the marginal part 4 can be tornoff along the tear-off line 3 with excellent shape precision.

<Tear-Aiding Structure>

The PSA sheet disclosed herein is provided with a tear-aiding structurealong a tear-off line that bounds a protection sheet part and a marginalpart, whereby the marginal part can be precisely torn off the protectionsheet part. The PSA sheet is configured so that the marginal part can betom off without using a cutting device such as a cutter. The tear-aidingstructure is not particularly limited as long as its form is useful insuch a tearing process. In other words, the tear-aiding structure in theart disclosed herein is not limited to the example shown in FIG. 1. Anyform is allowed as long as it is useful in facilitating the operation oftearing off the marginal part along the tear-off line or in increasingthe precision of the operation. Favorable examples of the tear-aidingstructure include cut holes and grooves. The tear-aiding structure inthe art disclosed herein may comprise one, two or more types of cutholes; one, two or more types of grooves; or a combination of these.

(Cut Holes)

As used herein, the cut hole(s) forming the tear-aiding structure referto line cut(s) or eyelet(s) made through the substrate and the conceptencompasses a perforation and a slit. The cut hole(s) may be formedbefore or after the PSA layer is placed on the substrate. From thestandpoint of the ease of application of a PSA composition, etc., in anembodiment, the cut hole(s) are preferably formed after the PSA layer isformed. In this case, the cut hole(s) may go through the substrate andalso the PSA layer or may go through the substrate and reach halfwaythrough the thickness of the PSA layer. Alternatively, the cut hole(s)may go through the substrate, but stops at the PSA layer.

The perforation refers to a row of cut holes arranged at certainintervals (with uncut sections) on the tear-off line, with each cut holehaving a length A and each uncut section having a length B at an A:Bratio in a range of 0.3:1 to 5:1. Here, the lengths A and B refer to thelengths along the tear-off line. The number of cut holes forming aperforation can typically be at least 3, for instance, at least 5. Themaximum number the cut holes is not particularly limited. The length Aof each cut hole forming the perforation is usually suitably 0.1 mm orgreater, or preferably 0.3 mm or greater, more preferably 0.5 mm orgreater. e.g. 1 mm or greater. From the standpoint of enhancing thehandling properties of the PSA sheet 1, for instance, inhibitingloosening and sagging of the PSA sheet in areas adjacent to cut holes,or even increasing the case of application, the upper limit of thelength A is usually suitably 20 cm or less, preferably 15 cm or less, ormore preferably 12 cm or less (e.g. 10 cm or less). In an embodiment,the length A of each cut hole forming the perforation can be less than10 mm, 7 mm or less, or even 5 mm or less.

The slit is a cut hole not included in the perforation and refers to,for instance, a cut hole that has a length A at a ratio (A:B) to thelength B of its adjacent uncut section of greater than 5:1 (e.g. 7:1,10:1.100:1, etc.). In view of the tear-aiding effects, the length A ofeach slit is usually suitably 2 mm or greater, or preferably 5 mm orgreater (e.g. 7 mm or greater). From the standpoint of the handlingproperties (e.g. the ease of application) of the PSA sheet 1, the upperlimit of the length A is usually suitably 20 cm or less, preferably 15cm or less, or more preferably 12 cm or less (e.g. 10 cm or less).

The uncut section, present possibly between cut holes forming theperforation or adjacent to a slit can be a non-processed segment of thetear-off line where the tear-aiding structure 30 is absent or a segmentwhere a groove (e.g. an incised mark) is formed as described later. Fromthe standpoint of enhancing the handling properties of the PSA sheet(e.g. inhibiting accidental tearing of the uncut section beforepurposeful tearing of the marginal part), the length of the uncutsection is usually suitably about 0.3 mm or greater, or preferably 0.5mm or greater (e.g. 0.7 mm or greater). When the uncut section is anon-processed segment, from the standpoint of the tearing precision, thelength of the uncut section is usually suitably 15 mm or less, orpreferably 10 mm or less, or it can be 7 mm or less, or even 5 mm orless (e.g. 3 mm or less). The tear-off line in the art disclosed hereinis preferably free of a non-processed segment longer than 15 mm over itsentire length (i.e. the entire length of the border line between theprotection sheet part and the marginal part). On the other hand, when agroove (e.g. an incised mark) is formed in the uncut section, themaximum length of the uncut section is not particularly limited.

The method for forming the cut hole(s) is not particularly limited. Forinstance, a method using a known perforating machine or slitting machinecan be employed. The process of forming the cut hole(s) can be done onthe first side of the substrate or on the second side (the back side).When the cut hole(s) are formed after the PSA layer is placed on thesubstrate, from the standpoint of preventing PSA accumulation on themachine blade, a method where the substrate is processed from the backside of the substrate can be preferably employed.

(Grooves)

As used herein, the groove(s) forming the tear-aiding structure refer todepression(s) in, but not through the substrate. The groove(s) can bethought as places where the thickness of the substrate is partiallysmaller as compared to the surroundings (typically the both sides of thetear-off line). With these grooves formed on the tear-off line, tearingof the PSA sheet proceeds along the grooves, preventing the tearing fromtaking place off the designated tear-off line (i.e. preventing thetearing from proceeding in an unexpected direction), whereby aprotection sheet can be formed with a precise shape. In addition, thePSA sheet can be smoothly split along the grooves; and therefore, theappearance of the edges in the resulting protection sheet tends to beimproved. For instance, fraying and splintering possibly caused duringthe tearing process by partial stretching of the resin film forming thesubstrate can be effectively reduced.

Here, the concept of groove encompasses a practically widthless formsuch as an incised mark formed by allowing a machine blade to penetratea substrate from the first face thereof to a certain depth but not allthrough the substrate followed by removing the machine blade. Examplesof other forms of the groove include a depression formed by scoring orimprinting (pressing). The incised mark can be preferably used becauseit is highly effective in facilitating precise tearing of the substratealong the tear-off line. The groove (e.g. an incised mark) can be formedbefore or after the PSA layer is placed on the substrate. From thestandpoint of the ease of applying the PSA composition, etc., in anembodiment the groove can be preferably formed after the PSA layer isformed.

The groove depth relative to the thickness of the substrate can beselected to obtain suitable tear-aiding effects, and is not particularlylimited. In an embodiment, the groove depth can be, for instance, 5% ormore of the thickness of the substrate. From the standpoint of obtaininggreater tear-aiding effects, it can be preferably 20% or more, morepreferably 40% or more, e.g. 60% or more. From the standpoint of thehandling properties of the PSA sheet, the groove depth is usuallysuitably 95% or less (preferably 85% or less. e.g. 80% or less) of thethickness of the substrate. The groove can be formed so that thethickness of the substrate at the groove bottom (i.e. the thickness fromthe groove bottom to the surface on the reverse side of the substrate)is, for instance, 2 μm or greater. From the standpoint of the handlingproperties of the PSA sheet the thickness of the substrate at the groovebottom is usually suitably 5 μm or greater (e.g. 7 μm or greater). Themaximum thickness of the substrate at the groove bottom is notparticularly limited. It can be, for instance, 30 μm or less, or even 20μm or less.

The groove length is not particularly limited. For instance, when thegroove length is 5 mm or greater (preferably 7 mm or greater, e.g. 10 mmor greater), the effects of the groove can be obtained to a greaterextent. In an embodiment, the groove length can be 50 mm or greater, oreven 100 mm or greater.

The method for forming the groove is not particularly limited. Forinstance, it is possible to employ a method using a known incisiondevice, scoring device, pressing device, etc. When the groove is formedby pressing, it can be formed on one side of the substrate, on the otherside (on the back side), or at corresponding locations on each side ofthe substrate. When an incised mark or a scored groove is formed,especially when the groove is formed after the PSA layer is formed, fromthe standpoint of the tear-aiding effects and the ease of processing,the groove is preferably formed on the back side of the substrate.

(Design of Tear-Aiding Structure)

Although no particular limitations are imposed, several preferableexamples of designs (machining patterns) of the tear-aiding structureare described.

As the tear-aiding structure, the PSA sheet disclosed herein preferablyhas a cut hole at least partially at the tearing start edge (the edgewhere tearing of the marginal pan starts). The tearing start edge cantypically be one of the edges of the length direction of the protectionsheet part. The cut hole(s) can be a perforation or a slit. The tearingstart edge may be provided with both a perforation and a slit. With thisfeature, tearing of the marginal part proceeds smoothly and theprotection sheet is prevented from lifting off the adherend. The tearingstart point prescribed by the pre-formed cut hole(s) can help startaccurate tearing along the tear-off line. Thus, upon tearing of themarginal part, a protection sheet with a precise outer shape can beformed. A favorable example of the tear-aiding structure includes aperforation or a slit provided over almost the entire width (e.g. 75% ormore of the width, preferably 85% or more) of the tearing start edge.

In a preferable embodiment, the tear-aiding structure can include agroove formed at least partially over a segment running from the tearingstart edge to the tearing finish edge of the marginal part, that is, thelength of a lateral side of the tear-off line. With such a structuralfeature, even when the speed of tearing the lateral side (the speed ofpulling the marginal part) is increased the resulting protection sheettends to have a highly precise shape and a good appearance. This isadvantageous in view of increasing the efficiency of applying protectionsheets. The groove may be provided to the entire length of the lateralside or only to a partial length of the lateral side, combined with, forinstance, a perforation or a slit. In view of possibly decreasing thenumber of uncut sections, a slit is more advantageous than a perforationas the cut hole(s) formed at the lateral side. When a perforation and/ora slit are formed at the lateral side, grooves provided to the uncutsections can improve the appearance of cut edges, whereby the resultingprotection sheet may have a highly precise shape. Although no particularlimitations are imposed, in an embodiment, the tear-aiding structure canbe generally the same between the two lateral sides. This allows tearingof the marginal part to proceed generally in the same manner at the twolateral sides, thereby increasing the workability.

In a preferable embodiment, for instance, as in Pattern 7 in Examplesdescribed later, the tear-aiding structure may include a cut hole(typically a slit) positioned continuously or adjacently to the tearingstart edge of the marginal part which is an edge of a lateral side ofthe tear-off line, and a groove (typically an incised mark) formedcontinuously or adjacently to the tearing finish edge of the cut hole.According to the PSA sheet in such an embodiment, the cut hole at thetearing start edge of a lateral side effectively dictates the directionin which tearing of the PSA sheet proceeds on the lateral side; andtearing of the PSA sheet on the lateral side is then allowed to proceedalong the groove placed continuously or adjacently to the tearing finishend of the cut hole; whereby a protection sheet with a highly preciseshape and a good appearance can be obtained more certainly andefficiently. Herein, that the cut hole is adjacent to an edge on thetearing start edge side may typically mean that the distance from theedge to the end of the cut hole is 7 mm or less, preferably 5 mm orless, e.g. 3 mm or less. That the groove is adjacent to an edge of thetearing finish edge side may typically mean that the distance from theedge to the end of the groove is 7 mm or less, preferably 5 mm or less,e.g. 3 mm or less.

The tear-aiding structure is not particularly limited at the tearingfinish edge of the marginal part. In an embodiment, the tear-aidingstructure can be generally the same at the tearing start edge and thetearing finish edge. This allows tearing to proceed in an arbitrarylength direction of the protection sheet part as desired, thereby makingthe PSA sheet convenient for use.

The PSA sheet disclosed herein can be preferably made in an embodimentwhere the tear-off line forms a shape that has a segment running in themachine direction (MD) of the resin film forming the substrate of thePSA sheet, or simply the MD of the PSA sheet. The resin film isgenerally susceptible to tearing in a direction along its MD. Thus, itis suitable for a use mode in which the marginal part is tom off bypulling the marginal part in a peel direction of the PSA sheet. Here,that the tear-off line runs in the MD of the PSA sheet means that theangle between the MD and the direction in which the tear-off line runsis 45° or smaller (preferably 30° or smaller, more preferably 150 orsmaller). According to the PSA sheet having a tear-off line in which thesegment that runs continuously in such a direction is 50 mm or longer(e.g. 100 mm or longer), particularly great effects can be obtained byapplying the art disclosed herein. It is preferable that a lateral side(i.e., running from the tearing start edge to the tearing finish edge)of the tear-off line has the segment that runs in such a direction. In aparticularly preferable embodiment, the lateral side has a groove, morepreferably the groove continuous or adjacent to the cut hole at thetearing start edge. In a long PSA sheet, usually, the resin film's MDgenerally coincides with the length direction of the PSA sheet.

The PSA sheet disclosed herein can be preferably made in an embodimentwhere the tear-off line is designed so that the MD of the PSA sheet,which may typically be the length direction in a long PSA sheet, is thelength direction of the protection sheet part. According to such anembodiment, by pulling the marginal part of the PSA sheet generallyalong the MD, the marginal part can be easily and precisely tom off toform a nice-looking protection sheet.

In the tear-off line of the PSA sheet disclosed herein, it is preferablethat a lateral side of the tear-off line, which is a segment of thetear-off line running from the tearing start edge to the tearing finishedge, is free of a part where the direction in which the segment runsturns to the tearing start edge side. In other words, the lateral sidesegment of the tear-off line is preferably free of a part where an anglelarger than 90° is formed between the straight line (possibly almostparallel to the MD of the PSA sheet) running from the tearing start edgeto the tearing finish edge and the direction in which the lateral sideruns. This angle is preferably 60° or smaller (more preferably 45° orsmaller, e.g. 30° or smaller). When the lateral side segment of thetear-off line has a part where the angle is larger than 60°, it ispreferable that a cut hole (e.g. a slit) is formed at the turning pointof the segment as the tear-aiding structure. By this, regardless of thepresence of such a part, the resulting protection sheet tends to have ahighly precise circumferential shape and a good appearance.

<Tensile Modulus> (Tensile Modulus E_(R))

In the PSA sheet having a groove as the tear-aiding structure, the resinmaterial forming the groove bottom in the substrate is not particularlylimited in tensile modulus (or bottom elastic modulus, hereinafter)E_(R). From the standpoint of improving the handling properties of thePSA sheet before applied to an adherend, the bottom elastic modulusE_(R) is preferably 200 MPa or greater. The bottom elastic modulus E_(R)can be, for instance, 200 MPa to 4000 MPa, 200 MPa to 2000 MPa, or even200 MPa to 1000 MPa.

In a preferable embodiment, the bottom elastic modulus E_(R) can be 300MPa or greater. When the PSA sheet is torn in the thickness directionalong the groove, a higher bottom elastic modulus E_(R) can effectivelyreduce frays and splinters which can be formed when the resin materialforming the groove bottom is partially stretched. Thus, the resultingprotection sheet tends to have a highly precise shape and a goodappearance. From such a standpoint, the bottom elastic modulus E_(R) canbe 400 MPa or higher, or even 500 MPa or higher. In an embodiment, thebottom elastic modulus E_(R) can be 650 MPa or higher, or even 750 MPaor higher. The bottom elastic modulus E_(R) can be adjusted by thecomposition of the resin material forming the groove bottom, theproduction method and conditions of the resin film, etc.

(Tensile Modulus E_(T))

The tensile modulus (or overall elastic modulus, hereinafter) E_(T) ofthe entire resin film forming the substrate is not particularly limited.From the standpoint of enhancing the handling properties of the PSAsheet before applied to an adherend, the overall elastic modulus E_(T)is preferably 200 MPa or higher (e.g. 200 MPa to 4000 MPa).

In an embodiment of the art disclosed herein, a preferable substrate mayhave an overall elastic modulus E_(T) of 2000 MPa or lower, morepreferably 1500 MPa or lower, e.g. 1000 MPa or lower. With decreasingoverall elastic modulus E_(T), the curved surface conformability of theprotection sheet formed from the PSA sheet using the particularsubstrate tends to increase. From such a standpoint, the substrate mayhave an overall elastic modulus E_(T) of 800 MPa or lower, or even 700MPa or lower.

In an embodiment, a preferable substrate may have an overall elasticmodulus E_(T) of 300 MPa or higher, more preferably 400 MPa or higher,e.g. 500 MPa or higher. With increasing overall elastic modulus E_(T) ofthe substrate, the shape precision and the appearance of the protectionsheet formed upon tearing of the marginal part tend to increase. In thePSA sheet having a non-processed segment (e.g. possibly present betweencut holes forming perforations or slits, or between a cut hole and agroove), it is particularly meaningful to increase the overall elasticmodulus E_(T) to inhibit fraying and splintering at the non-processedsegment. The overall elastic modulus E_(T) can be adjusted by thecomposition of the resin material forming the resin film the structureof the resin film, the production method and conditions of the resinfilm, etc. In a substrate formed with a monolayer resin film, the bottomelastic modulus E_(R) and the overall elastic modulus E_(T) are thesame.

The tensile moduli (bottom elastic modulus E_(R) and overall elasticmodulus E_(T)) refer to the tensile moduli determined based on JIS K7161, using, as a measurement sample, a monolayer resin film formed of aresin material forming the part of interest. In particular, with the MDbeing the length direction, the resin film is cut to a 10 mm wide stripto prepare a test piece. Based on JIS K 7161:1994, at 23° C. and 50% RH,the test piece is stretched at a tensile speed of 300 mm/min, at a chuckdistance of 50 mm to obtain a stress-strain curve. The tensile elasticmodulus can be determined by linear regression of the curve between twoprescribed strain points ε1 and ε2. The same method is also employed inExamples described later. The thickness of the resin film used as themeasurement sample is not particularly limited. It is usually suitableto use a resin film having a thickness of about 20 μm to 100 μm (e.g.about 40 μm).

<180° Peel Strength>

In the PSA sheet disclosed herein, the 180° peel strength (or simply thepeel strength, hereinafter) of the protection sheet part is notparticularly limited. From the standpoint of adequately protecting theadherend surface, for instance, it is usually suitably about 0.5 N/25 mmor greater, typically about 1 N/25 mm or greater. In a preferableembodiment, the protection sheet part of the PSA sheet can have a peelstrength of, for instance, 3 N/25 mm or greater, 4 N/25 mm or greater,or even 5 N/25 mm or greater. With the protection sheet having at leasta certain level of peel strength, when the marginal part is torn off bypulling it in a peel direction, the protection sheet part is less likelyto lift off the adherend surface, whereby stable tearing of the marginalpart is facilitated. This may increase the circumferential shapeprecision and the appearance of the protection sheet formed upon thetearing. From the standpoint of the ease of redoing the application whenapplying the protection sheet part to an adherend and of theremovability when peeling the PSA sheet off the adherend after it hasfinished serving for protection, the peel strength of the PSA sheet isusually suitably 20 N/25 mm or less, or preferably 15 N/25 mm or less(e.g. 10 N/2 mm or less).

The 180° peel strength of the protection sheet part is determined asfollows: In particular, the protection sheet part of the PSA sheet iscut to a 25 mm wide strip to prepare a measurement sample. In anenvironment at 23° C. and 50% RH, the adhesive face of the measurementsample is press-bonded to the surface of a stainless steel plate (SUS430BA plate) with a 2 kg roller moved back and forth once. The resultant isleft standing in the same environment for 30 minutes. Subsequently,using a tensile tester, based on JIS Z 0237:2000, the peel strength(N/25 mm) of the measurement sample is determined at a tensile speed of300 mm/min at a peel angle of 180°. As the tensile tester, for instance,a tensile/compression tester TG-lkN (available from Minebea Co., Ltd.)can be used. The same method is also used in Examples described later.For instance, the peel strength of the protection sheet part can beadjusted by the composition and the thickness of the PSA layer.

In an embodiment where the marginal part of the PSA sheet has a PSAlayer, the peel strength of the marginal part is not particularlylimited. For instance, the peel strength of the marginal part can becomparable to the peel strength of the protection sheet part.

<Positioning Assistant>

The PSA sheet disclosed herein may include a positioning assistant toassist positioning of the PSA sheet. The positioning assistant cantypically be thought as a feature that is useful in putting theprotection sheet part in place on an adherend with proper alignment. Aslong as it can serve such a function, the form of the positioningassistant is not particularly limited. The positioning assistant can be,for instance, a structural feature that is provided to the PSA sheetwhere it is in a certain location relative to the protection sheet partand is engaged with an alignment guide for proper alignment. Favorableexamples of the structural feature include a though hole, a notch, adepression and a protrusion provided to the PSA sheet. These types ofpositioning assistant are preferably placed in the marginal part. Thisenables efficient positioning of the protection sheet without impairingthe protective function of the protection sheet part. For the PSA sheetin a roll form, from the standpoint of the workability, as in theexample shown in FIG. 1, it is preferable to select an embodiment wherepositioning assistants are placed on the front edge side of the PSAsheet relative to the protection sheet part. The form of the positioningassistant is not limited to this example. For instance, it can be anoptically detectable marking (e.g. a coloration printed or directlymarked), an arranged separate member (e.g. an adhered identificationlabel, a fixed element that allows signal transmission or reflection),etc. As long as its form (e.g. the marking, etc.) does not impair theprotective function of the protection sheet part, the positioningassistant can be provided to the protection sheet part or to both themarginal part and the protection sheet part.

<Dimensions, Etc. of PSA Sheet>

The PSA sheet disclosed herein can have a width in accordance with thedimensions of the protected region so that the marginal part can be tornoff the protection sheet part in corresponding dimensions, and the widthis not particularly limited. From the standpoint of the ease ofapplication to adherends, the width of the PSA sheet is usually suitablyabout 150 cm or less, preferably 100 cm or less, or possibly 80 cm orless (e.g. 60 cm or less). The width of the PSA sheet can be, forinstance, 5 cm or greater, 10 cm or greater, or even 20 cm or greater.

The length of the PSA sheet (typically wound in a roll) disclosed hereincan be, for instance, 1 m or greater, 5 m or greater, or even 10 m orgreater. In an embodiment, the length of the PSA sheet can be 100 m orgreater (e.g. 200 m or greater, or even 300 m or greater). A longer PSAsheet can be provided with a larger number of protection sheet parts inthe length direction. In other words, a larger number of protectionsheets can be installed using one PSA sheet roll. This decreases thefrequency of changing PSA sheet rolls, thereby increasing theproductivity of adherends (e.g. members) bearing protection sheets. Themaximum length of the PSA sheet is not particularly limited. Forinstance, it can be 2000 m or less.

In the PSA sheet disclosed herein, the dimensions of the protectionsheet part can be designed in accordance with the dimensions of theprotected region to which the protection sheet part is applied, and arenot particularly limited. For instance, the protection sheet part mayhave dimensions such that the smallest rectangle enclosing theprotection sheet part has a long side length L_(x) of 5 cm or greater.According to an embodiment where the length L_(x) is 10 cm or greater(e.g. 20 cm or greater), the effects of placing protection sheets byapplying the art disclosed herein (e.g. one, two or more effects amongmore efficient placement of protection sheets, greater shape precision,and greater appearances) can be obtained to a greater extent. From thestandpoint of the ease of tearing off the marginal part, the maximumlength L_(x) is usually suitably 150 cm or less, or it can be 100 cm orless (e.g. 80 cm or less). The smallest rectangle enclosing theprotection sheet part may have a shape where the long side length L_(x)is equal to the short side length L_(y), that is, a square shape.

The protection sheet part may have a shape such that the long sidelength L_(x) is 1.0 times to 100 times the short side length L_(y) inthe smallest rectangle enclosing the protection sheet part. The artdisclosed herein can be preferably implemented in an embodiment wherethe long side L_(x) may be equal to or greater than 1.05 times the shortside length L_(y). In a preferable embodiment, the long side lengthL_(x) may be equal to or greater than 1.2 times (more preferably 1.5times, e.g. 2 times) the short side length L_(y). With the protectionsheet part having such a shape, greater significance may be seen intearing the marginal part off the protection sheet part by applying theart disclosed herein. The long side length L_(x) can be equal to orgreater than 5 times or even 10 times the short side length L_(y). In anembodiment, the long side length L_(x) can be equal to or less than 50times or even 30 times the short side length L_(y).

The protection sheet part in the PSA sheet disclosed herein can beoriented so that in the smallest rectangle enclosing the protectionsheet part, the angle between a long side thereof and the lengthdirection of the PSA sheet or the MD of the resin sheet forming thesubstrate of the PSA sheet is about 45° or smaller (preferably about 30°or smaller, more preferably about 15° or smaller. e.g. 5° or smaller).The angle can be substantially 0°.

The dimensions of the marginal part surrounding the protection sheetpart bounded by the tear-off line are not particularly limited. Forinstance, from the standpoint of the ease of tearing off the marginalpart by pulling it after the protection sheet part is applied to anadherend (e.g. in view of the ease of holding and the strength of themarginal part), the width of the narrowest part of the marginal part isusually suitably 5 mm or greater, or it can be preferably 10 mm orgreater, or more preferably 20 mm or greater. From the standpoint ofreducing wastes, the width of the narrowest part of the marginal partcan be, for instance, 500 mm or less.

<Substrate>

The substrate of the PSA sheet disclosed herein comprises a resin filmas the primary component. The PSA sheet formed with such a substrate issuited for a use mode as described earlier in which the marginal part ofthe PSA sheet is pulled in a peel direction to tear it off, with theprotection sheet part adhered on an adherend. With the protection sheetpart left on the adherend, a protection sheet suited to protect theadherend can be formed. As used herein, the substrate comprises a resinfilm as the prima component means that the resin film accounts for morethan 50% of the substrate by weight. The substrate formed with the resinfilm, possibly having a surface subjected to a surface treatment such asrelease treatment and primer coating, is a representative example of thesubstrate that comprises a resin film as the primary component. Theresin film forming the substrate may have a monolayer structure or amultilayer structure.

As used herein, the resin film refers to a film obtainable by molding afilm from a resin composition primarily comprising a resin as thosedescribed below; its concept is distinguished from so-called non-wovenfabrics and woven fabrics (i.e. the concept excludes non-woven fabricsand woven fabrics). A substantially non-foamed resin film is preferable.Here, the non-foamed resin film refers to a resin film that has not beensubjected to an intentional foaming process. In particular, it can be aresin film having an expansion ratio below about 1.1 (e.g. below 1.05,typically below 1.01).

Examples of the resin forming the resin film include polyolefinic resin(polyethylene, polypropylene, ethylene-propylene copolymer,ethylene-vinyl acetate copolymer, etc.), polyester-based resin(polyethylene terephthalate, polybutylene terephthalate, polyethylenenaphthalate, polybutylene naphthalate, etc.), vinyl chloride resin(typically soft vinyl chloride resin), vinyl acetate resin,polyurethane-based resin (ether-based polyurethane, ester-baserpolyurethane, carbonate-based polyurethane, etc.), urethane(meth)acrylate, thermoplastic elastomer (olefinic elastomer,styrene-based elastomer, acrylic elastomer, etc.), polycarbonate resin,polyamide resin and polyimide resin. These resins can be used singly asone species or in a combination of two or more species.

The PSA sheet disclosed herein can be preferably made in an embodimenthaving a substrate that comprises, for instance, a polyolefinic resinfilm or a polyester-based resin film as the primary component. Aparticularly preferable substrate comprises a polyolefinic resin film asthe primary component. Here, the polyolefinic resin film refers to aresin film whose primary component is polyethylene (PE) resin and/orpolypropylene (PP) resin. The polyolefinic resin film may comprise PEresin and PP resin in a combined amount of greater than 50% (preferably70% or more, e.g. 85% or more) by weight of the polyolefin resin film.

The primary component of the PP resin can be a propylene-based polymerof various types comprising propylene as a monomer. The PP resin may beessentially formed of one, two or more species of propylene-basedpolymer. Besides homopolypropylenes, the concept of propylene-basedpolymer encompasses a random polypropylene (random copolymer ofpropylene and other monomer(s)) and a block polypropylene (blockcopolymer of propylene and other monomer(s)). For instance, the conceptof propylene-based polymer here includes the following species:

Propylene homopolymers (homopolypropylenes) such as isotacticpolypropylenes;

Random copolymers (random polypropylenes) of propylene and otherα-olefin(s) (typically, one, two or more species selected from ethyleneand α-olefins having 4 to 10 carbon atoms); preferably, randompolypropylenes formed from propylene as the primary monomer (the mainmonomer, i.e. a component accounting for at least 50% by weight of allmonomers).

Block copolymers (block polypropylenes) obtained by blockcopolymerization of propylene and other α-olefin(s) (typically, one, twoor more species selected from ethylene and α-olefins having 4 to 10carbon atoms); preferably, block polypropylenes comprising propylene asthe primary monomer (the main monomer, i.e. a component accounting forat least 50% by weight of all monomers).

The primary component of the PE resin can be an ethylene-based polymerof various types comprising ethylene as a monomer. It can be a PE resinessentially formed of one, two or more species of ethylene-basedpolymer. The ethylene-based polymer can be an ethylene homopolymer or acopolymerization product (e.g. random copolymer or block copolymer) ofethylene as the primary monomer and other α-olefin(s) as the secondarymonomer(s). Preferable examples of the α-olefin include α-olefins with 3to 10 carbon atoms such as propylene, 1-butene (possibly a branched1-butene), 1-hexene, 4-methyl-1-pentene, and 1-octene. For instance, apreferable PE resin comprises, as the primary component, anethylene-based polymer in which an α-olefin as the secondary monomer iscopolymerized up to 10% (typically up to 5%) by weight.

The PE resin can be obtainable by copolymerization of ethylene and afunctional monomer (a monomer containing other functional group(s) inaddition to a polymerizing functional group), by copolymerization ofsuch a functional monomer with an ethylene-based polymer, etc. Examplesof a copolymer of ethylene and a functional monomer includeethylene-vinyl acetate copolymers (EVA), ethylene-acrylic acidcopolymers (EAA), ethylene-methacrylic acid copolymers (EMAA),ethylene-methyl acrylate copolymers (EMA), ethylene-ethyl acrylatecopolymers (EEA), ethylene-methyl methacrylate copolymers (EMMA), andethylene-(meth)acrylic acid copolymers (i.e., copolymers obtainable fromethylene and acrylic acid and/or methacrylic acid) crosslinked by metalions.

The density of the PE resin is not particularly limited. The concept ofPE resin here includes high-density polyethylene (HDPE), medium-densitypolyethylene (MDPE), low-density polyethylene (LDPE) and linearlow-density density polyethylene (LLDPE). In an embodiment, the PE resinhas a density of, for instance, about 0.90 g/cm³ to 0.94 g/cm³.Preferable PE resins include LDPE and LLDPE.

Although no particular limitations are imposed, as the polyolefin resinmaterial, a species having a MFR (melt flow rate) in a range of about0.5 g/10 min to 80 g/10 min (e.g. 0.5 g/10 min to 10 g/10 min) can bepreferably used. Here, the MFR refers to the value determined based onJIS K 7210 by method A at a temperature of 23° C. at an applied load of21.18 N.

The polyolefin resin film preferably comprises at least PP resin as thepolyolefin resin. For instance, a preferable polyolefin resin film has acomposition including at least 20% PP resin by weight (more preferablyat least 30% by weight). Such a composition can favorably bring about aresin film having a bottom elastic modulus E_(R) and an overall elasticmodulus E_(T) suited for preventing fraying and splintering.

In an embodiment, it is preferable to use a polyolefin resin film inwhich a continuous structure (a continuous phase) of PP resin is formed.In a multilayer resin film, at least one layer is preferably a layerhaving a continuous phase of a PP resin. The layer having a continuousphase of PP resin is preferably placed to form first and/or second facesof the resin film. With the use of the resin film in such an embodiment,when the tear-aiding structure includes a groove and the groove bottomis formed with the layer having a continuous phase of PP resin, theresulting protection sheet can have a highly precise shape and a goodappearance.

The number of layers in the multilayer resin film can be, for instance,about 2 to 5. For instance, a preferable resin film has a three-layerstructure with a front layer forming a first face (the surface on whichthe PSA layer is placed) of the substrate, a back layer forming a secondface (back face) of the substrate, and a middle layer placed betweenthem. In an embodiment, one or each (preferably each) of the front andback layers can be formed from a resin material having a higher tensilemodulus than that of the middle layer. Such an embodiment can bringabout a PSA sheet more favorably combining easy tear-off nature of themarginal part and curved surface conformability of the protection sheet.

Although no particular limitations are imposed, for instance, thethree-layer resin film can be formed so that the thickness of the middlelayer accounts for about 20% to about 80% (preferably about 30% to about70%) of the overall thickness of the resin film. In an embodiment, thefront and back layers can be generally comparable in thickness. Forinstance, the thickness of the front layer is preferably about 0.5 timesto 1.5 times the thickness of the back layer. The front and back layerscan have essentially the same thickness.

To the resin film, inorganic powder can be added as necessary. This canblock light such as UV rays to inhibit photodegradation of the substrateand the PSA layer. As the inorganic powder, oxides such as titaniumoxide, zinc oxide, magnesium oxide, alumina and silica; carbonates suchas calcium carbonate; sulfates such as barium sulfate; and the like canbe used.

A favorable example of the inorganic powder is titanium dioxide (TiO₂).The type of titanium dioxide is not particularly limited. For instance,titanium dioxide in any crystal form such as rutile, anatase andbrookite can be used. In particular, rutile titanium dioxide ispreferable. Titanium dioxide having coated particle surfaces can be usedas well. The coating material of the titanium dioxide particles is notparticularly limited. For instance, it can be an inorganic oxide such assilica, alumina and zinc oxide. Favorable examples include highlyweather-resistant titanium dioxide (typically rutile titanium dioxide)having particle surfaces coated with Si—Al₂O₃, etc.

From the standpoint of obtaining good light-blocking effects, the amountof the inorganic powder added is suitably 5% by weight or more of theentire substrate, preferably 6% by weight or more, or more preferably 7%by weight or more. In view of the strength and the ease of molding ofthe substrate, etc., the inorganic powder content is suitably 30% byweight or less of the entire substrate, preferably 20% by weight orless, or more preferably 15% by weight or less. In the multilayer resinfilm, the inorganic powder may be added only to some of the layers or toall layers in the same proportions or in different proportions.

To the substrate, as necessary, known additives that can be used inplastic film for PSA sheet substrates can be suitably added, such asweatherability enhancers (UV absorber, antioxidant, photostabilizer,etc.), antistatic agent and slip agent. Examples of photostabilizerinclude those containing benzotriazoles, hindered amines and benzoatesas active ingredients. Examples of antioxidant include those containingalkylphenols, alkylene bisphenols, thiopropionic acid esters, organicphosphorous acid esters, amines, hydroquinones and hydroxylamines asactive ingredients. These additives can be used singly as one species orin a combination of two or more species. The additives can be added inamounts about the same as usual amounts in resin film for PSA sheetsubstrates.

The thickness of the substrate is not particularly limited and can besuitably selected in accordance with the purpose. For instance, asubstrate having a thickness of about 300 μm or less can be used. Fromthe standpoint of the conformability to contours of the adherendsurface, etc., the thickness of the substrate can be, for instance, 200μm or less, or it is suitably 100 μm or less, preferably 75 μm or less,or more preferably 50 μm or less. The thickness of the substrate can be,for instance, 10 μm or grater. From the standpoint of the strength, thehandling properties and the light-blocking properties, it is suitably 15μm or greater, preferably 20 μm or greater, or more preferably 25 μm orgreater (e.g. 30 μm or greater).

The polyolefin resin film may be obtained by molding a sheet by aheretofore known method from a resin material that comprises resinsincluding a polyolefin resin, inorganic powder and other materials(additives, etc.) used as necessary. For example, the polyolefin resinfilm can be produced by suitably employing a heretofore known generalfilm-molding method such as extrusion molding and inflation molding.From the standpoint of the ease of tearing off the marginal part and theappearance of the protection sheet etc., an extrusion method can bepreferably used as the method for forming the resin film.

The face of the substrate to be provided with the PSA layer may besubjected to a known or commonly used surface treatment such as coronadischarge treatment, plasma treatment. UV ray irradiation, acidtreatment, alkali treatment and primer coating. Such a surface treatmentmay enhance adhesion between the substrate and the PSA layer, that is,the anchoring of the PSA layer to the substrate. In a preferable surfacetreatment, a polar group such as hydroxy group (—OH) is introduced tothe front face of the substrate. This can increase the anchoring of thePSA layer and further increase the anti-residue properties.

The second face (back face) of the substrate opposite from the faceprovided with the PSA layer may be subjected, as necessary, to a surfacetreatment such as antistatic treatment, release treatment and waterrepellent treatment. The release treatment provided to the back face ofthe substrate brings about effects such as easier unwinding of the PSAsheet wound in a roll, etc. The release treatment may involve formationof a release layer on the back face of the substrate using various typesof release agent such as silicone-based, long-chain alkyl-based,fluorine-based release agents and molybdenum sulfide.

<PSA Layer>

The type of PSA forming the PSA layer in the PSA sheet disclosed hereinis not particularly limited. For instance, the PSA layer may compriseone, two or more species of PSA selected among various known PSAs suchas a rubber-based PSA (natural rubber-based, synthetic rubber-based,their mixture-based, etc.), acrylic PSA, polyester-based PSA,urethane-based PSA, polyether-based PSA, silicone-based PSA,polyamide-based PSA, and fluorine-based PSA. Here, the rubber-based PSArefers to a PSA comprising a rubber-based polymer as the base polymer.The same applies to the other PSAs. The base polymer of a PSA refers tothe primary component among rubbery polymers (polymers that exhibitrubber elasticity in a room temperature range) in the PSA, typically acomponent that accounts for more than 50% (e.g. possibly 70% or more, oreven 90% or more) by weight of the polymers.

(Rubber-Based PSA)

In a preferable embodiment, the PSA layer is a rubber-based PSA layerformed of a rubber-based PSA comprising a rubber-based polymer as thebase polymer (the primary component among polymers). Examples of thebase polymer in a rubber-based PSA include various rubber-based polymerssuch as natural rubber, styrene-butadiene rubber (SBR); polyisoprene;butyl rubbers such as regular butyl rubber, chlorinated butyl rubber,and brominated butyl rubber isobutylene-based polymers such aspolyisobutylene, isoprene-isobutylene copolymer and a modified productthereof; an A-B-A block copolymer rubber and a hydrogenation productthereof, such as a styrene-butadiene-styrene block copolymer rubber(SBS), styrene-isoprene-styrene block copolymer rubber (SIS),styrene-vinylisoprene-styrene block copolymer rubber (SVIS),styrene-ethylene-butylene-styrene block copolymer rubber (SEBS) which isa hydrogenation product of SBS, and styrene-ethylene-propylene-styreneblock copolymer rubber (SEPS) which is a hydrogenation product of SIS.

The art disclosed herein can be preferably implemented in an embodimentcomprising a PSA layer formed of a non-crosslinked PSA. Examples of thenon-crosslinked PSA include a PSA comprising an ABA-type block copolymerrubber or its hydrogenation product as the base polymer, a PSAcomprising an isobutylene-based polymer as the base polymer, and thelike. Among these, a preferable PSA layer is constituted with apolyisobutylene-based non-crosslinked PSA formed from a PSA compositioncomprising an isobutylene-based polymer as the base polymer. Anon-crosslinked PSA layer is less likely to apply stress on the surfaceof an adherend and also less likely to leave adhesion marks. Thus, it isfavorable as the PSA layer for the protection sheet

The isobutylene-based polymer may be an isobutylene homopolymer(homopolyisobutylene) or a copolymer based on isobutylene as a primarymonomer. Examples of the copolymer include a copolymer of isobutyleneand normal butylene, copolymer of isobutylene and isoprene (regularbutyl rubber, chlorinated butyl rubber, brominated butyl rubber,partially crosslinked butyl rubber, etc.), vulcanized products ormodified products of these (e.g. products modified with a functionalgroup such as hydroxyl group, carboxyl group, amino group, epoxy group,etc.), and the like. From the standpoint of the stability of adhesivestrength (e.g., non-susceptibility to an excessive increase in theadhesive strength due to aging or a thermal history), preferably usableisobutylene-based polymers include a isobutylene homopolymer and anisobutylene-normal butylene copolymer. In particular, a isobutylenehomopolymer is preferable.

The molecular weight of the isobutylene-based polymer is notparticularly limited. For instance, an isobutylene-based polymer havinga weight average molecular weight (Mw) of about 1×10 to 150×10⁴ can besuitably selected and used. Two or more isobutylene-based polymershaving individually different Mw values may be used in combination. As awhole, the isobutylene-based polymer for use has a Mw value in a rangeof preferably about 10×10⁴ to 150×10⁴, more preferably about 30×10⁴ to120×10⁴, typically 40×10⁴ to 105×10⁴, e.g. about 50×10⁴ to 100×10⁴.

The polyisobutylene-based PSA may comprise, as its base polymer(s), one,two or more species selected from these isobutylene-based polymers. Inaddition to the base polymer, the polyisobutylene-based PSA maycomprise, as a secondary component, a non-polyisobutylene-based polymer.Examples of such a polymer include a poly(meth)acrylic acid ester,polybutadiene, polystyrene, polyisoprene, polyurethane,polyacrylonitrile, polyamide, etc. The non-polyisobutylene-based polymercontent is usually preferably 10% by weight or less of the total polymercontent in the polyisobutylene-based PSA. The PSA may be essentiallyfree of a non-polyisobutylene-based polymer.

The PSA can include a tackifier as necessary. Examples of preferablyusable tackifiers include tackifier resins such as rosin-based resins,terpene-based resins, petroleum resins, phenol resins, alkylphenolresins, xylene resins, coumarone-indene resins, alkyd resins, epoxyresins, and hydrogenation products of these. These tackifiers can beused singly as one species or in a suitable combination of two or morespecies.

In a preferable embodiment, the PSA disclosed herein may comprise atackifier resin T_(hs) having an SP value of 8.5 or higher (in(cal/cm³)^(1/2); the same applies hereinafter). As the tackifier resinT_(hs), for instance, a tackifier resin having an SP value in a range of8.5 to 15 can be preferably used. For instance, a phenolic compound, anamine-based compound, a rosin-based resin (e.g. unmodified rosin) andthe like having such SP values can be used as the tackifier resinT_(hs). For the tackifier resin T_(hs), solely one species or a suitablecombination of two or more species can be used. Such a tackifier resinT_(hs) can be used in a small amount and may effectively increase theadhesive strength. Thus, it is suited for combining higher adhesivestrength to an adherend and a lower risk of contamination on theadherend surface.

Here, the SP value indicates the solubility of a compound and is a valuedetermined from the basic structure of the compound by the methodproposed by Fedors. In particular, from the vaporization energy Δe (cal)of each atom or atomic group at 25° C. as well as the molar volume Δv(cm³) of the atom or atomic group at the same temperature, the SP valueis determined by the next equation:

SP value(δ)=(ΣΔe/ΣΔv)^(1/2)

(Reference: Hideki Yamamoto. “SP value fundamentals, application, andcalculation method” (4th edition) published by Johokiko Co., Ltd., Apr.3, 2006. pp. 66-67).

Favorable examples of the phenolic compound that can be used as thetackifier resin T_(hs) include phenol resins, alkylphenol resins,rosin-modified phenolic resins and terpene-modified phenol resins. Apreferable alkyl phenol resin has a side-chain alkyl group with three ormore carbon atoms (typically with 3 to 18. e.g. 5 to 12 carbon atoms),such as tert-butylphenol resin, tert-amylphenol resin andtert-octylphenol resin. A favorable example of the tackifier resinT_(hs) used in the PSA in the at disclosed herein is a phenolic compoundhaving an SP value of 9.5 or higher (typically 9.5 to 15. e.g. 10 to15). An example of the phenolic compound is trade name DUREZ 19900available from Sumitomo Durez Co., Ltd. In typical, the tackifier resinT_(hs) is a material whose purpose does not involve UV ray absorption,or radical trapping or stabilization in a photodegradation reaction.Thus, the tackifier resin T_(hs) is distinguished from materialsgenerally used as antioxidant or photostabilizer.

In an embodiment using a tackifier, its amount used can be, forinstance, about 0.1 to 50 parts by weight relative to 100 parts byweight of the base polymer. It is usually preferable that the amountadded relative to 100 parts by weight of the base polymer is 0.1 to 5parts by weight. Alternatively, the PSA may have a compositionessentially free of a tackifier.

When a tackifier resin T_(hs) with a high SP value is used, its amountused is usually suitably 5 parts or less (e.g. 2.5 parts or less) byweight to 100 parts by weight of the base polymer, or preferably 1.0part or less (typically, 0.01 part to 1.0 part) by weight. The artdisclosed herein can be preferably implemented in an embodiment wherethe tackifier resin T_(hs) content in the PSA is 0.8 part or less (morepreferably 0.5 part or less, e.g. 0.01 part to 0.4 part) by weight to100 parts by weight of the base polymer. From the standpoint ofobtaining favorable effects of the tackifier resin T_(hs), the lowerlimit of the tackifier resin T_(hs) content is preferably 0.05 part orhigher (e.g. 0.1 part or higher, typically 0.2 part or higher) by weightto 100 parts by weight of the base polymer.

(Acrylic PSA)

In another preferable embodiment, the PSA layer is an acrylic PSA layerformed of an acrylic PSA comprising an acrylic polymer as the basepolymer. Such an acrylic PSA layer can be preferably used from thestandpoint of the transparency, etc.

A preferable acrylic polymer is, for instance, a polymer formed from astarting monomer mixture that comprises an alkyl (meth)acrylate as theprimary monomer and possibly a secondary monomer copolymerizable withthe primary monomer. Here, the primary monomer refers to a componentthat accounts for more than 50% by weight of the total monomer contentin the starting monomer mixture. As used herein, the (meth)acrylatecomprehensively refers to acrylate and methacrylate.

As the alkyl (meth)acrylate, for instance, a compound represented by theformula (1) below can be suitably used:

CH₂═CR¹COOR²  (1);

Here. R¹ in the formula (1) is a hydrogen atom or a methyl group. R² isan acyclic alkyl group having 1 to 20 carbon atoms (hereinafter, such arange of the number of carbon atoms may be indicated as C₁₋₂₀). From thestandpoint of the storage elastic modulus of the PSA, etc., an alkyl(meth)acrylate herein R² is a C₁₋₁₄, (e.g. C₂₋₁₀, typically C₄₋₉)acyclic alkyl group is preferable. An alkyl acrylate wherein R₁ is ahydrogen atom and R² is a C₄₋₉ acyclic alkyl group is more preferable.

Examples of the alkyl (meth)acrylate wherein R¹ is a C₁₋₂₀ acyclic alkylgroup include methyl (meth)acrylate, ethyl (meth)acrylate, propyl(meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate,isobutyl (meth)acrylate, s-butyl (meth)acrylate, pentyl (meth)acrylate,isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate,2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl(meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl(meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, lauryl(meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate,pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl(meth)acrylate, octadecyl (meth)acrylate, nonadecyl (meth)acylate andeicosyl (meth)acrylate. These alkyl (meth)acrylates may be used singlyas one species or in a combination of two or more species. Particularlypreferable alkyl (meth)acrylates include n-butyl acrylate (BA) and2-ethylhexyl acrylate (2EHA). Preferably, either BA or 2EHA can be usedalone or the two can be used in combination.

The primary monomer content in all the monomers is preferably about 70%by weight or higher (e.g. about 85% by weight or higher, typically about90% by weight or higher). It is usually preferably about 99.5% by weightor lower (e.g. about 99% by weight or lower). When a C₄₋₉ alkyl acrylateis used as a monomer, the C₄₋₉ alkyl acrylate content of the alkyl(meth)acrylates in the monomers is preferably about 70% by weight orhigher, more preferably about 90% by weight or higher, or yet morepreferably about 95% by weight or higher. It can be about 99% by weightor higher, and about 100% by weight or lower. In a preferableembodiment, the monomers include at least BA or 2EHA. The art disclosedherein can be preferably implemented, for instance, in an embodimentwhere the combined amount of BA and 2EHA is about 50% by weight or more(typically about 70% by weight or more, e.g. about 90% by weight ormore) of all the monomers.

The secondary monomer copolymerizable with the alkyl (meth)acrylate asthe primary monomer may be useful for introducing crosslinking pointsinto the acrylic polymer and for increasing the cohesive strength of theacrylic polymer. As the secondary monomer, one, two or more species canbe used among functional group-containing monomers such as carboxygroup-containing monomers, hydroxy group-containing monomers, acidanhydride group-containing monomers, amide group-containing monomers,amino group-containing monomers, keto group-containing monomers,monomers having N-containing rings, alkoxysilyl group-containingmonomers, imide group-containing monomers, and epoxy group-containingmonomer. From the standpoint of increasing the cohesive strength, etc.,an acrylic polymer in which a carboxy group-containing monomer and/or ahydroxy group-containing monomer are copolymerized as the secondarymonomer is preferable. Favorable examples of the carboxygroup-containing monomer include acrylic acid and methacrylic aid.Favorable examples of the hydroxy group-containing monomer includehydroxyalkyl (meth)acrylates such as 2-hydroxyethyl acrylate and4-hydroxybutyl acrylate.

The amount of the secondary monomer can be suitably selected to obtaindesirable cohesive strength and is not particularly limited. Usually,from the standpoint of combining well-balanced adhesive strength andcohesive strength, the amount of the secondary monomer is suitably about0.5% by weight or more of the total monomer content in the acrylicpolymer, or preferably about 1% by weight or more. The amount of thesecondary monomer is usually suitably about 30% by weight or less of thetotal monomer content, or preferably about 15% by weight or less (e.g.about 10% by weight or less).

In the acrylic polymer, other monomer(s) may be copolymerized as far asthe effects of the invention are not impaired. For instance, these othermonomers can be used for adjusting the glass transition temperature ofthe acrylic polymer, adjusting the adhesive properties (e.g.removability), etc. Examples of a monomer that may increase the cohesivestrength of the PSA include sulfonate group-containing monomers,phosphate group-containing monomers, cyano group-containing monomers,vinyl esters (vinyl acetate, vinyl propionate, vinyl laurate, etc.), andaromatic vinyl compounds. These other monomers can be used singly as onespecies or in a combination of two or more species. The other monomercontent is preferably about 30% by weight or less (e.g. about 10% byweight or less) of the total monomer content. For instance, it can beabout 0.01% by weight or more (typically about 0.1% by weight or more).

The method for obtaining the acrylic polymer is not particularlylimited. The polymer can be obtained by applying various polymerizationmethods generally used for acrylic polymer synthesis, such as solutionpolymerization, emulsion polymerization, bulk polymerization, andsuspension polymerization. The acrylic polymer can be a randomcopolymer, a block copolymer, a graft copolymer, etc. From thestandpoint of the productivity etc., a random copolymer is usuallypreferable.

The acrylic PSA can be formed, using a PSA composition that furthercomprises, in addition to the acrylic polymer, a known crosslinkingagent, for instance, an epoxy-based crosslinking agent, isocyanate-basedcrosslinking agent, silane-based crosslinking agent, oxazoline-basedcrosslinking agent, aziridine-based crosslinking agent, and metalchelate-based crosslinking agent. For the crosslinking agent, solely onespecies or a suitable combination of two or more species can be used.The amount of the crosslinking agent used is not particularly limited.It can be selected to obtain desirable cohesive strength. Usually, theamount of the crosslinking agent used to 100 parts by weight of theacrylic polymer is suitably about 0.05 part to 10 parts (preferably 0.1part to 10 parts, more preferably 0.3 part to 7 parts, e.g. 1 part to 5parts) by weight.

To the PSA (e.g. a rubber-based PSA, an acrylic PSA, etc.) in the artdisclosed herein, suitable components (additives) allowed for inclusionin the PSA can be added as necessary. Examples of the additives includesoftener, release-aiding agent, pigment or fillers, antioxidant, andphotostabilizer. The concept of photostabilizer encompasses radicalscavenger and UV ray absorber. These additives can be used singly as onespecies or in a combination of two or more species. The additives can beused, for instance, in amounts about the same as usual amounts added inthe field of PSA used for protection sheets.

The PSA layer in the art disclosed herein may be formed from, forinstance, a water-dispersed PSA composition, a solvent-based PSAcomposition, a hot-melt PSA composition or an active energy ray-curablePSA composition. The PSA layer can be formed based on a method forforming PSA layers known in the PSA sheet field. For instance, a directmethod can be employed where the PSA composition is directly provided(typically applied) to the substrate and allowed to dry. Alternatively,a transfer method can be employed where the PSA composition is providedto a releasable surface (e.g. a release liner surface, the back face ofa substrate pre-subjected to release treatment, etc.) and allowed to dryto form a PSA layer on the surface and the PSA layer is transferred tothe substrate.

The thickness of the PSA layer is not particularly limited and can besuitably selected in accordance with the purpose. From the standpoint ofthe tightness of adhesion to the adherend surface, the thickness of thePSA layer is usually suitably 2 μm or greater, or preferably 3 μm orgreater. In an embodiment, from the standpoint of likely obtainingadhesive strength (peel strength) suited for stable tearing of themarginal part, the thickness of the PSA layer is preferably 5 μm orgreater (e.g. 7 μm or greater). From the standpoint of the removabilityand inhibiting an increase in adhesive strength with aging, thethickness of the PSA layer is usually suitably 100 μm or less, orpreferably 30 μm or less, or it can also be 20 μm or less (e.g. 15 μm orless).

<Applications>

No particular limitations are imposed to the type of adherend (theobject to be protected) to which the protection sheet part of the PSAsheet disclosed herein is applied. The adherend may have a surfaceformed of, for instance, a metallic material such as stainless steel(SUS), aluminum, and zinc-plated steel plate; an inorganic material suchas glass and ceramic; a resin material such as polycarbonate resin,acrylic resin (typically, polymethyl methacrylate resin (PMMA)), cyclicpolyolefin resin, phenol resin, acrylonitrile butadiene styrenecopolymer (ABS), acrylonitrile styrene acrylate copolymer (ASA),polyphenylene ether resin, polystyrene resin, polyolefinic resin such aspolyethylene and polypropylene, and polyethylene terephthalate (PET); arubber material such as natural rubber, synthetic rubber, acrylicrubber, thermoplastic elastomer (e.g. olefinic thermoplastic elastomer,styrene-based thermoplastic elastomer); and a composite material ofthese. The adherend surface can also be a coated surface with anacrylic, polyester-based, alkyd-based, melamine-based, urethane-based,acid-epoxy crosslinking-based, their composite-based (e.g. acrylicmelamine-based, alkyd melamine-based) paint, etc.

The adherend may be a material, a molded body, a component (member), aproduct and so on, formed using aforementioned materials. Although noparticular limitations are imposed, the PSA sheet disclosed herein canbe preferably used for protection purposes of various members. Forinstance, it is favorable in an application where the protection sheetformed from the protection sheet part of the PSA sheet is placed on thesurface (the surface to be protected) of a member. A favorable exampleof the member is a member constituting a vehicle such as an automobile.Non-limiting examples of the vehicle constituting member include anexterior panel, a pillar, a window frame, an interior material, and astructural material of a vehicle body.

The surface state of the adherend is not particularly limited. In viewof easy pulling and tearing of the marginal part after the protectionsheet part of the PSA sheet is applied to the adherend, it can bepreferably applied to an object to be protected having a smooth flatsurface. For instance, a preferable adherend is the surface of a memberhaving a smooth flat surface formed of a resin material (e.g. acrylicresin, ABS resin, polystyrene resin, etc.) or a glass material.

The matters disclosed herein includes the following:

-   -   (1) A PSA sheet comprising a substrate and a PSA layer placed on        a first face of the substrate, wherein

the PSA sheet comprises a protection sheet part to be adhered to anadherend to protect the adherend, a marginal part bounded from theprotection sheet part by a tear-off line surrounding the protectionsheet part, and a tear-aiding structure provided along the tear-offline;

the substrate comprises a resin film as its primary component, and

the PSA sheet is configured so that after the protection sheet part isadhered to the adherend, when the marginal part is pulled in a directionin which the PSA sheet is peeled off the adherend, the marginal part istom off the protection sheet part.

(2) The PSA sheet according to (1) above, being long and wound in aroll.

(3) The PSA sheet according to (1) or (2) above, wherein the surface ofthe PSA layer is separably in contact with the back face of the PSAsheet.

(4) The PSA sheet according to any of (1) to (3) above, comprising aplurality of the protection sheet parts serially arranged in the lengthdirection of the PSA sheet.

(5) The PSA sheet according to any of (1) to (4) above, wherein thetear-aiding structure comprises at least a cut hole or a groove.

(6) The PSA sheet according to any of (1) to (5) above, wherein thetear-aiding structure comprises a groove running along the tear-offline.

(7) The PSA sheet according to (6) above, wherein the groove is formedon the back side of the substrate.

(8) The PSA sheet according to (6) or (7) above, wherein the groovebottom in the substrate is formed with a resin material having a tensilemodulus of 300 MPa or greater.

(9) The PSA sheet according to any of (1) to (8) above, wherein thetear-aiding structure comprises a cut hole placed at a tearing startedge of the marginal part.

(10) The PSA sheet according to (9) above, wherein the tear-aidingstructure comprises a groove formed continuously or adjacently to thecut hole placed at the tearing start edge of the marginal part.

(11) The PSA sheet according to any of (1) to (10) above, wherein thesubstrate comprises a polyolefinic resin film as the resin film.

(12) The PSA sheet according to any of (1) to (11) above, wherein theprotection sheet part exhibits a 180° peel strength of 3 N/25 mm orgreater.

(13) The PSA sheet according to any of (1) to (12) above, comprising aplurality of application units divided by separation lines.

(14) The PSA sheet according to (13) above, wherein each of theplurality of application units comprises at least one each of theprotection sheet part and the marginal part surrounding the protectionsheet part.

(15) The PSA sheet according to (13) or (14) above, being long and woundin a roll wherein the plurality of application units are seriallyarranged in the length direction of the PSA sheet divided by separationlines running across the width of the PSA sheet.

(16) The PSA sheet according to any of (13) to (15) above, comprisingseparation-aiding structures formed along the separation lines.

(17) The PSA sheet according to any of (1) to (16) above having apositioning assistant to assist positioning of the PSA sheet.

(18) The PSA sheet according to (17) above, wherein the positioningassistant is provided to the marginal part.

(19) The PSA sheet according to any of (1) to (18) above, wherein theprotection sheet part has a shape such that in the smallest rectangleenclosing the protection sheet part, the long side length L_(x) is equalto or greater than 1.05 times the short side length L_(y).

(20) The PSA sheet according to any of (1) to (19) above, wherein, inthe smallest rectangle enclosing the protection sheet part, a long sidethereof and the length direction of the PSA sheet or the MD of the resinsheet forming the substrate of the PSA sheet forms an angle of 45° orsmaller

(21) The PSA sheet according to any of (1) to (20) above, wherein thesubstrate has a thickness of 10 in or greater and 100 μm or less (e.g.25 μm or greater and 75 μm or less).

(22) The PSA sheet according to any of (1) to (21) above, wherein thePSA layer has a thickness of 3 μm or greater and 30 μm or less (e.g. 5μm or greater and 15 μm or less).

(23) The PSA sheet according to any of (1) to (22) above, wherein thePSA layer is formed from a non-crosslinked PSA.

(24) A method for producing a protection sheet-bearing member in which aprotection sheet is adhered to a surface of a member, the methodcomprising:

obtaining a PSA sheet comprising a substrate whose primary component isa resin film and a PSA layer placed on a first face of the substratewherein the PSA sheet comprises a protection sheet part to be adhered toan adherend to protect the adherend, a marginal part bounded from theprotection sheet part by a tear-off line surrounding the protectionsheet part, and a tear-aiding structure provided along the tear-offline;

adhering the protection sheet part to the member, and

pulling the marginal part in a direction in which the PSA sheet ispeeled off the member thereby tearing the marginal part off theprotection sheet part leaving the protection sheet part on the member.

(25) A method for applying a protection sheet to a surface of a member,the method comprising:

obtaining a PSA sheet that comprises a substrate whose primary componentis a resin film and a PSA layer placed on a first face of the substratewherein the PSA sheet comprises a protection sheet part to be adhered toan adherend to protect the adherend, a tear-off line surrounding theprotection sheet part, and a marginal part bounded from the protectionsheet part by the tear-off line, and further comprises a tear-aidingstructure provided along the tear-off line;

adhering the protection sheet part to the member, and

pulling the marginal part in a direction in which the PSA sheet ispeeled off the member, thereby tearing the marginal part off theprotection sheet to leave the protection sheet on the member.

EXAMPLES

Several worked examples relating to the present invention are describedbelow, but the present invention is not intended to be limited to theseexamples. In the description below, “parts” and “%” are based on weightunless otherwise specified.

In the respective Examples, the following substrates and PSAcompositions were used.

(Substrate S1)

Using a T-die film molder, a mold material (PP/PE) containing 70 partsof PP (homopolypropylene under trade name NOVATEC PP FY4 available fromJapan Polypropylene Corporation. MFR=5.0; the same applies hereinafter)and 30 parts of PE (linear low density polyethylene (LLDPE) under tradename KERNEL KF380 available from Japan Polypropylene Corporation,density d=0.925 g/cm³; the same applies hereinafter) was melted,kneaded, and extruded to obtain a 40 μm thick monolayer resin film. Theback face of the resin film was treated with a long-chain alkyl releaseagent and the resultant was used as a substrate S1.

For each of the mold materials used in fabricating the substrate S1 andthe following substrates S2 to S6, to 100 parts of the resin material,was added 10 parts of TiO₂ (Si—Al₂O₃-coated rutile titanium dioxideunder trade name TIPAQUE CR-95 available from Ishihara Sangyo Kaisha,Ltd.).

(Substrate S2)

Using a T-die film molder, PP and PE w-re melted, kneaded, andco-extruded in three layers to obtain a three-layer resin film (40 μmthick) having a middle layer formed of PE between back and front layersformed of PP. The back middle and front layers were 10 μm, 20 μm and 10μm in thickness, respectively. The back face of the resin film wassubjected to the same release treatment as the substrate S1 and theresultant was used as a substrate S2.

(Substrate S3)

Using a T-die film molder, PP and PE were melted, kneaded, andco-extruded in three layers to obtain a three-layer resin film (40 μmthick) having a middle layer formed of PP between back and front layersformed of PE. The back middle and front layers were 10 μm, 20 μm and 10μm in thickness, respectively. The back face of the resin film wassubjected to the same release treatment as the substrate S1 and theresultant was used as a substrate S3.

(Substrate S4)

Using a T-die film molder, PP was extruded to obtain a 40 μm thickmonolayer resin film. The back face of the resin film was subjected tothe same release treatment as the substrate S1 and the resultant wasused as a substrate S4.

(Substrate S5)

Using a T-die film molder, PE was extruded to obtain a 40 μm thickmonolayer resin film. The back face of the resin film was subjected tothe same release treatment as the substrate S1 and the resultant wasused as a substrate S5.

(Substrate S6)

Using a T-die film molder, a mold material (PP/PE) containing 70 partsof PP and 30 parts of PE and a mold material (PE/PP) containing 70 partsof PE and 30 parts of PP were melted, kneaded and extruded to obtain athree-layer resin film (40 μm thick) having a middle layer formed ofPP/PE between back and front layers formed of PE/PP. The back, middleand front layers were 10 m, 20 μm and 10 μm in thickness, respectively.The back face of the resin film was subjected to the same releasetreatment as the substrate S1 and the resultant was used as a substrateS6.

(Substrate S7)

The back face of trade name LUMIRROR S105 (38 μm thick) available fromToray Industries, Inc. was subjected to the same release treatment asthe substrate S1 and the resultant was used as a substrate S7.

The overall elastic moduli E_(T) of the substrates according to therespective Examples were determined by the method described earlier.With respect to each three-layer substrate, the resin material forforming its front layer was used to form a 40 μm thick monolayer resinfilm. Using this resin film as a measurement sample, the bottom elasticmodulus E_(R) was determined by the method described earlier. Theresults are shown in Tables 1 and 2. Here, as the bottom elastic modulusE_(R) of a monolayer substrate, the same value as the overall elasticmodulus E_(T) of the substrate is shown.

(PSA Composition A1)

In an organic solvent, was dissolved a polyisobutylene (trade nameOPPANOL N80 available from BASF Corporation) to prepare a PSAcomposition A1.

(PSA Composition A2)

In a reaction vessel equipped with a condenser, nitrogen inlet,thermometer and stirrer, a monomer mixture containing 50 parts of2-ethylhexyl acrylate, 50 parts of n-butyl acrylate, 5 parts of acrylicacid and 1 part of 2-hydroxyethyl acrylate was allowed to undergosolution polymerization at 60° C. for 6 hours under nitrogen flow, intoluene as the polymerization solvent, using 2,2′-azabisisobutyronitrileas the polymerization initiator, to obtain a toluene solution of acrylicpolymer (30% solid). To the toluene solution, to 100 parts of theacrylic polymer in the solution, was admixed 0.5 part of an epoxy-basedcrosslinking agent (trade name TETRAD C available from Mitsubishi GasChemical Co., Inc.) to prepare a PSA composition A2.

(PSA Composition A3)

The amount of the epoxy-based crosslinking agent used to 100 parts ofthe acrylic polymer was changed to 2 parts. Otherwise in the same manneras the preparation of the PSA composition A2, was prepared a PSAcomposition A3.

<Fabrication of PSA Sheets> Example 1

The PSA composition A1 was applied to the adhesive face-side surface ofthe substrate S1 and allowed to dry at 80° C. for one minute to form a10 μm thick PSA layer. The resultant was cut to a 60 cm long, 30 cm widerectangular shape to obtain a non-processed PSA sheet (free of atear-aiding structure). Here, the vertical direction of the PSA sheetwas in the MD (i.e. the extrusion direction) of the substrate.Subsequently, in the central part of the non-processed PSA sheet,Pattern 1 described later was formed by machining, by a process to forma tear-aiding structure, along a rectangular tear-off line (20 cm long,10 cm wide). A processed PSA sheet according to the present Example wasthus obtained.

With respect to the PSA sheet of Example 1 and the PSA sheets accordingto Examples 2 to 7 and 9 to 17 below, in addition to one of Patterns 1to 7 as a tear-aiding structure, a round through hole of 10 mm diameterwas also formed at each corner of one edge of the length direction (onewidthwise edge) of each PSA sheet as a positioning assistant.

Examples 2 to 8

Instead of Pattern 1, the patterns shown in Table 1 were formed.Otherwise in the same manner as Example 1, were obtained processed PSAsheets according to Examples 2 to 8.

Example 9

As Example 9, the non-processed PSA sheet was used.

Examples 10 to 14

In place of the substrate S1, the substrates shown in Table 2 were used.Otherwise in the same manner as Example 7, were obtained PSA sheetsaccording to Examples 10 to 14.

Examples 15 to 17

The substrates and the PSA compositions shown in Table 2 were used.Otherwise in the same manner as Example 7, were obtained PSA sheetsaccording to Examples 15 to 17.

<Machining Patterns> (Pattern 1)

Short side (the same for each of the two sides): A90 mm long slit wasformed, leaving 5 mm at each end.

Long side (the same for each of the two sides): Two 90 mm long slitswere formed, spaced apart by 10 mm, leaving 5 mm at each end.

(Pattern 2)

The tear-off line was perforated over the entire length. The length A ofeach cut hole forming the perforation was 3 mm and the space B betweencut holes was 2 mm (i.e. A:B=1.5:1). The perforation process was carriedout on the back side of the substrate, using a known perforatingmachine.

(Pattern 3)

A machine blade was allowed to penetrate the substrate on the back sideto form a 30 μm deep incised mark over the entire length of the tear-offline.

(Pattern 4)

Short side (the same for each of the two sides): A perforation similarto Pattern 2 was formed over the entire length.

Long side (the same for each of the two sides): An incised mark similarto Pattern 3 was formed over the entire length.

(Pattern 5)

Short side (the same for each of the two sides): A perforation similarto Pattern 2 was formed over the entire length.

Long side (the same for each of the two sides): Similarly to the longside of Pattern 1, two 90 mm long slits were formed, spaced apart by 10mm, leaving 5 mm at each end.

(Pattern 6)

Incised marks similar to Pattern 3 were formed along the tear-off lineso as to connect adjacent slits in Pattern 1.

(Pattern 7)

Short side (the same for each of the two sides): A perforation similarto Pattern 2 was formed along the entire length.

Long side (the same for each of the two sides): A 10 mm long slit wasformed at each end and an incised mark (180 mm long) similar to Pattern3 was formed between the slits.

(Pattern 8)

In the rectangular tear-off line in Pattern 7, 180 mm long centralstretch of each long side (i.e. where the incised mark was formed inPattern 7) was offset 10 mm to one side of the short sides to modify theline shape so that each end of the long side central stretch (i.e. eachend of the incised mark) is connected to a short side with an arc-shapedslit of 10 mm radius.

<Application (Adhesion) Test>

Using a PMMA plate (20 cm long, 10 cm wide rectangle) as the adherend,the PSA sheet according to each Example was placed with the tear-offline aligned with the circumference of the PMMA plate. The area insidethe tear-off line (the protection sheet part) in the PSA sheet waspress-bonded to the PMMA plate. Subsequently, by hand-holding themarginal part of each PSA sheet (a portion of the PSA sheet hanging offthe PMMA plate at the other edge of the length direction, i.e. the edgeon the opposite side from where the positioning assistants were formed),the PSA sheet was pulled in the length direction at an angle of about120° to 150° to the surface of the PMMA plate, whereby the marginal partwas torn off the protection sheet part. Then, the periphery of theprotection sheet formed from the protection sheet part left on the PMMAplate was visually inspected. With respect to each Example, theapplication test was conducted three times and the performance of thePSA sheet was evaluated in the aspects described below.

(Ease of Application)

The ease of application of the protection sheet part was evaluated basedon the following four grades:

E: No problem with application (excellent ease of application)

G: Some extra time taken for placement adjustments and redoing theapplication occasionally (good ease of application)

A: Some extra time taken for occasional attention required in handlingthe PSA sheet (practically acceptable ease of application)

P: Application not possible without touching the adhesive face of theprotection sheet part (poor ease of application)

(Ease of Tearing)

The ease of tearing off the marginal part was evaluated based on thefollowing grades:

E: The marginal part torn off without stopping in the middle of theoperation (excellent ease of tearing)

G: Some extra time taken for occasional attention required in tearingoff the marginal part (good ease of tearing)

A: Some extra time taken for the protection sheet part needed to be helddown by hand while tearing off the marginal part (practically acceptableease of tearing)

P: A cutting device needed for tearing off the marginal part (poor easeof tearing)

(Appearance of Protection Sheet)

The appearance of the periphery of each protection sheet was evaluatedbased on the following four grades:

E: No splinters or frays found (excellent appearance)

G: A few splinters and frays found, but not significant (goodappearance)

A: Many or notably long splinters and frays found (practicallyacceptable appearance)

P: Protection sheet suffering damage to the circumferential shape due tosplinters and frays, unable to cover the entire range of the adherendsurface properly (failed appearance)

<Curved Surface Conformability>

As the adherend, was used a flat rectangular PMMA plate thermallydeformed to a three-dimensional shape having a vertical curvature of3000 mm and a horizontal curvature of 5000 mm. The non-processed PSAsheet according to each Example was cut to a 20 cm long, 10 cm widerectangular shape. The resultant was applied to the central part of theadherend at room temperature. After 30 minutes, the state of the sheetwas visually inspected. Based on the observations, the curved surfaceconformability was evaluated based on the following four grades:

E: No lifting of the protection sheet found anywhere in the protectionsheet (excellent curved surface conformability)

G: Slight partial lifting found at the periphery of the protection sheet(good curved surface conformability)

A: Obvious partial lifting found at the periphery of the protectionsheet (practically acceptable curved surface conformability)

P: Not conforming to the curved surface, peeling of the protection sheetfound (poor curved surface conformability)

The results are shown in Tables 1 and 2. Tables 1 and 2 also show thepeel strength of the PSA sheet according to each Example determined bythe method described earlier.

As shown in Tables 1 and 2, with respect to the PSA sheets of Examples 1to 8 and 10 to 17 having tear-aiding structures along the tear-offlines, all exhibited practically acceptable or higher levels of ease ofapplication and ease of tearing. Particularly good ease of tearing wasobserved with PSA sheets having machining patterns with cut holes at thetearing start edges. The PSA sheet of Example 17 having low peelstrength was susceptible to lifting of the protection sheet part duringtearing of the marginal part, showing a tendency to require a longerwork time as compared to other PSA sheets featuring the same machiningpattern.

In studies using the substrate S1, with PSA sheets having two slits perlateral side and PSA sheets having grooves (incised marks) as thetear-aiding structure at lateral sides of their tear-off lines(rectangles), nice-looking protection sheets were formed. A particularlygreat appearance was obtained in Example 6 provided with a tear-aidingstructure having both slits and grooves at the lateral sides. Withrespect to the PSA sheet according to Example 2, due to the presence ofseveral non-processed segments between perforated holes at the lateralsides, somewhat many frays were observed at the periphery of theprotection sheet. In Example 11, splinters were observed at the lateralsides of the protection sheet. In Example 12, splinters were observed atthe lateral sides and frays at both the tearing start edge and thetearing finish edge. However, these were not too extensive to impair theprotective functions of the protection sheets.

Although specific embodiments of the present invention have beendescribed in detail above, these are merely for illustrations and do notlimit the scope of the claims. The art according to the claims includesvarious modifications and changes made to the specific embodimentsillustrated above.

REFERENCE SIGNS LIST

-   1 PSA sheet-   1A adhesive face-   1B back face-   2 protection sheet part-   3 tear-off line-   3A, 3C short sides-   3B, 3D long sides-   4 marginal pan-   10 substrate-   10A first face-   10B second face (back face)-   12 front layer-   14 middle layer-   16 back layer-   30 tear-aiding structure-   32 cut bole (perforation, tear-aiding structure)-   34 cut bole (slit, tear-aiding structure)-   36 groove (incised mark, tear-aiding structure)-   36A bottom-   42 positioning assistant-   50 PSA layer-   90 adherend (object to be protected, member)-   100 PSA sheet roll-   100A, 100B application units-   102 separation line-   120 separation-aiding structure

1. A pressure-sensitive adhesive sheet comprising a substrate and apressure-sensitive adhesive layer placed on a first face of thesubstrate, wherein the pressure-sensitive adhesive sheet comprises aprotection sheet part to be adhered to an adherend to protect theadherend, a marginal part bounded from the protection sheet part by atear-off line surrounding the protection sheet part, and a tear-aidingstructure provided along the tear-off line, the substrate comprises aresin film as its primary component, and the pressure-sensitive adhesivesheet is configured so that after the protection sheet part is adheredto the adherend, when the marginal part is pulled in a direction inwhich the pressure-sensitive adhesive sheet is peeled off the adherend,the marginal part is torn off the protection sheet part.
 2. Thepressure-sensitive adhesive sheet according to claim 1 being long andwound in a roll, and comprising a plurality of the protection sheetparts serially arranged in the length direction of thepressure-sensitive adhesive sheet.
 3. The pressure-sensitive adhesivesheet according to claim 1, wherein the tear-aiding structure comprisesat least a cut hole or a groove.
 4. The pressure-sensitive adhesivesheet according to any one of claim 1, wherein the tear-aiding structurecomprises at least a groove running along the tear-off line.
 5. Thepressure-sensitive adhesive sheet according to any one of claim 1,wherein the groove bottom in the substrate is formed with a resinmaterial having a tensile modulus of 300 MPa or greater.
 6. Thepressure-sensitive adhesive sheet according to any one of claim 1,wherein the substrate comprises a polyolefinic resin film as the resinfilm.
 7. The pressure-sensitive adhesive sheet according to any one ofclaim 1, wherein the protection sheet part exhibits a 180° peel strengthof 3 N/25 mm or greater.
 8. The pressure-sensitive adhesive sheetaccording to any one of claim 1, comprising a plurality of applicationunits divided by separation lines, with each application unit comprisingat least one each of the protection sheet part and the marginal partsurrounding the protection sheet part.
 9. The pressure-sensitiveadhesive sheet according to any one of claim 1, wherein the marginalpart is provided with a positioning assistant to assist positioning ofthe pressure-sensitive adhesive sheet.
 10. A method for producing aprotection sheet-bearing member in which a protection sheet is adheredto the surface of the member, the method comprising: obtaining apressure-sensitive adhesive sheet comprising a substrate whose primarycomponent is a resin film and a pressure-sensitive adhesive layer placedon a first face of the substrate, wherein the pressure-sensitiveadhesive sheet comprises a protection sheet part to be adhered to anadherend to protect the adherend, a marginal part bounded from theprotection sheet part by a tear-off line surrounding the protectionsheet part, and a tear-aiding structure provided along the tear-offline; adhering the protection sheet part to the member; and pulling themarginal part in a direction in which the pressure-sensitive adhesivesheet is peeled off the member, thereby tearing the marginal part offthe protection sheet part leaving the protection sheet part on themember.
 11. A method for applying a protection sheet to a surface of amember, the method comprising: obtaining a pressure-sensitive adhesivesheet that comprises a substrate whose primary component is a resin filmand a pressure-sensitive adhesive layer placed on a first face of thesubstrate wherein the pressure-sensitive adhesive sheet comprises aprotection sheet part to be adhered to an adherend to protect theadherend, a marginal part bounded from the protection sheet part by atear-off line surrounding the protection sheet part, and a tear-aidingstructure provided along the tear-off line; adhering the protectionsheet part to the member, and pulling the marginal part in a directionin which the pressure-sensitive adhesive sheet is peeled off the member,thereby tearing the marginal part off the protection sheet part leavingthe protection sheet part on the member.